A strain of human cytomegalovirus called Towne was isolated in WI-38 human fibroblast cell cultures from the urine of an infected infant. It was then passaged 125 times in WI-38, including three clonings, and a pool was prepared in the same cell substrate for use as a potential live attenuated vaccine. The Towne virus has a broad antigenicity and cross-reacts with the AD-169 strain. Several markers of the Towne virus were found which differentiated it from fresh isolates. One of these was resistance of the former to trypsin. The Towne virus was tested for freedom from oncogenicity or other harmful effects in preparation for tests in humans.

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SummaryThe in vivo properties of the "Cendehill" strain of attenuated rubella virus were further studied. The absence of seroconversion in rabbits inoculated subcutaneously was confirmed. When the virus was given intravenously most rabbits seroconverted and virus could be recovered from the organs of inoculated animals. Virulent virus given subcutaneously even in minute amounts, regularly evoked antibodies.When given by the combined intrathalamic, intraspinal and intramuscular routes, the "Cendehill" strain evoked antibodies in about one third of Cercopithecus monkeys in 17 to 19 days. When cortisone was given simultaneously with the virus the seroconversion rate in monkeys inoculated under similar conditions dropped to about 3O/o . A depressive effect of cortisone on the production of antibodies was also observed when virulent virus or the attenuated RA27/3 virus were used.Comparative tests with virulent virus and "Cendehill" virus were also carried out in the following species: rats, mice, ferrets, gerbils and guinea-pigs. They all responded serologically to a single parenteral inoculation of wild virus. Mice, ferrets, gerbils and guinea-pigs failed to seroconvert when inoculated with "Cendehill" virus. The rat was the only species in which a seroconversion could be regularly obtained.

ExtractHigh passage Cendehill strain of rubella virus, possessing in vivo and in vitro characteristics of an attenuated virus, was tested for efficacy in 28 seronegative infants, 3 to 23 months old. Thirteen seronegative infants received one subcutaneous injection of 0.5 ml of the vaccine preparation containing 10 3 -7 plaque-forming units (PFU) per ml. Fifteen seronegative infants served as controls for viral spread and were kept in intimate contact with the vaccinees for a period of 6 weeks.All thirteen vaccinees developed high levels of hemagglutination-inhibiting antibodies, from V128 to VaiMs, confirming the immunogenicity of the vaccine. No clinical reactions were observed in the vaccinees. The fifteen contacts remained seronegative, indicating that no viral spread occurred from the vaccinees to the susceptible contacts.The present clinical trial provides evidence that high-passage Cendehill strain presents characteristics of immunogenicity, nonreactogenicity and noncommunicability, making it a prospective candidate for a live attenuated rubella virus vaccine. SpeculationWhen the results of preliminary immunization trials with the attenuated Cendehill strain of rubella virus are confirmed in larger groups, this strain may meet all the criteria required for a safe and efficient immunizing agent against rubella.